Telephone-exchange system



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- 0. H. KOPP TELEPHONE EXCHANGE SYSTEM 11 sheets-she'et 11 Filed Oct. 16 1924 1 Af/jn Patented June 22, 1926.-

UNITED STATES PATENT OFFICE.

OTTMAR H. KOPP, or BROOKLYN, NEW YORK, ASSIGNOR T0 WESTERN ELECTRIC COMPANY, INCORPORATED, on .NEW YORK, N. Y., A CORPORATION or NEW YORK.

'1IE'FLIEPI-IOI N E-IEIXCI'IAN'GIEI SYSTEM.

Application filed October 16, 1924. Serial No. 743,919.

This invention relates to telephone exchange systems and more particularly to systems employing automatic switches forthe extension of connections.

In telephone systems where the extension of connections is under the control of register senders, calls for special positions, such as wire chief, trouble man, business oflice, etc., have been accomplished by dialing a first digit from two to nine. This digit is followed by one or more ones, other digits being reserved to regular oflice codes. In areas where ofiice codes are made up'of a plurality of digits this arrangementis satisfactory since the digit one is never used in an oflice code. In exchange areas where the oflice code consists of a single digit, the use of such a code for obtaining connections to special positions would seriously limit the number of subscribers in an oflice, since the 1000 group and the 100 group could not be used for subscigiibers numbers as well as for an operators co e.

It is therefore an object of the present invention to provide codes of universal applicability for reaching such special positions in a telephone exchange.

A feature of the invention lies in utilizing a plurality of single pulses followed-by a series of pulses to direct calls to special positions.

Another feature of the invention lies in recording such single pulses on recording relays and the series of the pulses on the first of the registers.

A further feature of the invention lies in the setting of the translator under the joint control of said register and. said recording relays to extend calls to special positions at the telephone exchange. 4,

These and other features of the invention will be apparent from a consideration of the following description. It may be noted that the ofiice codes of the present application may be used in addition to those formerly in use in large exchange areas.

The present disclosure is based on an arrangement by which a start circuit common to a group of lines is associated with an idle sender and with an idle district selector by means of a link circuit. This arrangement is disclosed and claimed in U. S. Patent No. 1.567.072, granted December 29, 1925 to V. II. Matthies.

Referring to the drawings, Fig. 1 shows one of a group of subscribers lines together with the line and the trip circuit common to the group of lines, which serves to control a start circuit.

Fig. 2 shows thestart circuit serving a plurality of groups of lines. 7

Fig. 3 shows a line finder-district selector circuit for extending the line to subsequent selectors. r

Fig. 4 shows one of a plurality of link circuits serving the start circuit of Fig. 2 and having access to a plurality of line finderdistrict selector circuits such as shown in Fig. 3. A portion of two other link circuits are also shown. 1

Figs. 5, 6, 7, 8, 9 and 10 show the circuits of a sender adapted to be selected by link circuits such as shown in Fig. 4 and to control the setting of selector switches.

Fig. 11 shows in a diagrammatic manner the switches and apparatus necessary to extend a call to a subscriber in a full mechanicaloflice, to a subscriber in a manual office or to an operator.

Fig. 12 shows the manner in which Figs. 1 to 11 are to be arranged for a proper disclosure of the invention.

Brief description.

Before proceeding with the detailed description a brief statement as to the operation of the circuits will be given.

Subscribers lines such as line 100 are connected to multiple terminals appearing before a purality of line finders. These multiple terminals are arranged in a plurality of groups, each group being served by a separate brush set on each finder and each group being divided into two subgroups. A trip circuit is provided individual to each group; a start circuit is provided for all the groups of lines served by the group of line'finders;

and a plurality of link circuits are provided for each group of lines and line finders. The line finders and link circuits are divided into two subgroups and each such subgroup normally serves calls in the corresponding subgroups of lines. The arrangement is such that, except when all link circuits are busy, a particular link circuitwill be in readiness to serve a call and will be connected by its district finder to an idle line finder.

When a call is initiated by a subscriber in a particular group, the trip circuit individual to the group, and the start circuit are taken for use by that line and means are provided for preventing the extension of a call in the ot ier subgroup of the group or in any other group until a line finder has been started in search of this calling line. Means are also provided for preventing. the extension of a second call in this group until after simultaneous calls in other groups have been taken care of. Theoperation of thestart circuit causes the line finder as sociated with the linl: circuit allotted for use to hunt for the calling line and. also causesthe link circuit to hunt for anidle sender. As soon as a particular link is taken for use- With a call the netlink is allotted to serve the next incoming call in the particular subgroups Which they serve. As soon as brush set on the line finder has been tripped the start circuit will be freed to permit the extension of'calls in other groups. As soon the line has been found the trip circuit of the group is freed: by the line tinder to extend another call in-the same group provided no call is awaiting extension in another group. As soon as selections are con'ipletcd: the sender and linlr circuit are released by the district selector circuit: andthe link circuit immediately hunts for another idle district;

Dczfmled description.

hen the subscriber at substation 100' removes his receiver from the sivitchhook a circuit is closed for line relay 1 0L extending from battery through't hat relay, inner contact of relay 102 over the subscribers loop to ground at theo'uter contact of relay 102. Relay 101 operates and closes a circuit from battery, resistance 10%, through the Winding of relay 103 to ground at the outer contact of relay 101.

The operation of relay 1'03 closes a circuit from battery, resistance 105' to gr und atthe outer right contact of relay 108. This circuit is in shuntof the Winding of relay 106, which? relay serves the second subgroup of the group to which line 100 be longs, thus preventing the extension ofa callfrom that subgroup, hile the trip cir- 't is in use With line 100. The operation relay 103 also closes a cir uit trim bat-- tery', t; "roughthe Winding of-relay 200, con ductor 133, outer left contact of relay 107, outerin'os left contact of relay 103 to ground. in addition relay 103 closes a circuit from hatt :3, over the back contact of relay 201 condnctor'130, rigl'it winding of trip relay 108, inner left contact of relay 107, innermost left contact of relay 103, left contact of relay 109 to ground.

Relay 108 operates in this circuit and closes a locking circuit for itself from ground, right contact of relay 109, left Winding, and inner left contact of relay. 108, over the inner left back contact of the trip re lays of the other groups of lines, conductor 129, right Winding of start relay 201 to battery. Relay 201- operates inthis-circuit. A circuit is now closed for relay 110 extending from battery through the winding of relay 110,. right contact of relay 108, conductor 128, to ground at the outer right contact of relay201. Rela-y1-10' locks in an obvious circuit to ground at the leftback contactof relay 109. Relay 1053, together with relay 103 prepares a circuit from the outerv con-v tact of relay l-10,-outer left front contact of relay 108, inner right cont-actof relay 103, conductor 131, left back contact of relay 202, outer left back contact of relay 203, conductor. 206, upper Contact 01 02 ,111 101, upper contact ofcain 4:02 brush 161 and its associated terminal, conductor 3T8, upper contacts ofcam 301, Winding of relay 302, to battery, assuming that the line finder of Fig. had been allotted for use by the switch 160 andtihe sequence'sn'itch 300 is therefore standing in position p The operation of relay 108 also closes a circuit from ground over its outer right contact, through the winding of the trip magnet 303, serving the group in which line 100 appears on the line finder frame, to battery. Relay 110 upon energizing closes a circuit from batter', through the left Wind ing of relay 109, left Winding of relay 107, outer contact of relay 1.10 to ground. Relay 10'? operates and locks through its right Winding and inner rightcontact to the con tact ofrelay 200.. v

The operationof relay 302 closes acircuit from battery, througl'i the Winding of up drive magnet 30 i, middle left contact of relay 302, upper left contact of cam 364e, left front contact of relay 302 to und.

Under the control of the updrive magnet 304 the line finder shaft is moved upwards. Due to the operation of the trip magnet 303 the set of brushes serving, the group of lines to which line 100 belongs is tripped. When the magnet leaves, the trip ping zone a circuit is closed from ground over brush 307, tir-ough commutator segment 805, upper contacts of cam 306, outer left normal contact of key 204, inner right contact and right Winding of relay 201 to battery. Relay 201 is held operated in this circuit but the circuit through the locking Winding of relay 108 is shunted and that relay releases, in turn releasing the trip magnet 303. As soon as brush 307 leaves segment 305 the'circuit of relay 201 is opened andv that relay releases again connecting battery to the operating windings of relay 108 and the corresponding relays in othertrip circuits, so that subsequent calls'may be served.

. been found.

Relay 302 closes a locking circuit for itself over its inner left contact, right contact of cam 308, back contact of relay 320, commutator segment 321, brush 322, to ground, which is closed as soon as the line finder shaft moves upward. Relay 302 also closes a circuit from battery, over the inner left contact of relay 205, right winding of relay 203, conductor 207, left contacts of cam 403, brush 462, and its associated terncinal, conductor 379, upper left contact of cam 311, right front contact of relay 302 to ground. The operation of relay 203 removes ground from conductor 206 thus preventing the start of another line finder until the brushes are tripped. Relay 203 locks in a circuit from battery, over the outer left contact of relay 205, left winding and outer left front contact of relay 203, left back contact of relay 202, conductor 131, inner right contact of relay 103, outer left contact of relay 108, outer contact of relay 110 to ground. The operation of relay 203 also closes a locking circuit for relay 201 from battery, left contact and left, winding of relay 201, inner right contact of relay 203 to ground. The circuits just traced are established before relay 108 is released by the shunting action of commutator segment 305. As soon, however, as relay 108 deenergizes it'opens the locking circuit of relay 203, restoring the start circuit to condition to serve subsequent calls.

When relay 302 operates it also closes a circuit from ground through its right front contact, upper left contact of cam 311, conductor 379, brush 462, and its associated contact, right contact of'cam 404, upper left contact of cam 405, right winding of relay 406, winding of relay 407, upper left contact of earn 408, upper right contact of cam 409, resistance 410 to battery. ,Relays 406 and 407 operate, relay 406 closing a locking circuit for itself and relay 407 from battcry, through resistance 410, upper right contact of cam 409, upper left contact of cam 408, winding of relay 407, right winding of relay 406, contact of cam 411, contact of relay 406 to ground. Relay 407 operates in this locking circuit and closes a circuit from battery, through the winding of sequence switch magnet 400, upper contact of cum 412, contact of relay 407 to ground. Magnet 400 operates advancing the link circuit sequence switch to position 2.

In position 2 ground is connected from the right contact of cam 415 to brush 466 and its associated contact, conductor 375, lower right contact of cam 312, lower right contact of cam 313, left winding of relay 314 to battery. Relay 314 operates, but performs no function until the calling line has Ground from the front contact of relay 406 is also extended over the contact of cam 411, upper left contact of cam 405, upper right contact of cam 404, left contacts of cam 403, conductor 207, right winding of relay 203, inner left contact of relay 205 to battery, holding relay 203 operated until the link circuit is moved out of position 1. arrives in position 2 relays 406 and 407 release. The release of relay 407 completes a circuit from ground at the back contact of relay 407, upper right and lower left contact of cam 405, winding of magnet 487 to battery. Magnet 487 operates and closes an obvious circuit for magnet 488. Magnet 488 is the rotary magnet for sender selector switch 480 and causes the switch to rotate in search of an idle sender.

An idle sender is characterized by the connection of battery, through a 150 ohm resistance, such as resistance 501, to conductor 502 and its corresponding terminal in the set engaged by brush 483. VVit-h the link circuit sequence switch in position 2 ground is connected over the upper right contact of cam 421, through the left winding of relay 406, lower contact of cam 413, right Winding of relay 406, winding of relay 407, lower contact of cam 401, lower right contactof cam 402 to brush 483.

When brush 483 encounters a terminal corresponding to an idle sender, to which battery is connected, relay 406 operates, short circuiting its left hand winding over its contact and the contact of cam 411, per mitting relay 407 to operate in series with the right hand winding of relay 406. The operation of relay 407 opens the circuit ofv magnet 487 and (loses a circuit from battcry through the winding of sequence switch magnet 400, upper contact of cam 412, front contact of relay 407 to ground advancing the link sequence switch to position 3.

In position 3 a circuit is prepared extending from ground through the right and middle windings of relay 503, inner left contact of relay 504, right back contact of relay 505, conductor 506, brush 484 of sender selector 480, lower left and upper right contacts of cam 408, brush 464 of district finder 460 to conductor 315, left contact of cam 316,,

left winding of relay 317 to battery, which 1 vVhen the link circuit 380, brush 381, right contact of cam 318,

contact of relay 320, commutator segment 321, brush to ground. Relay 109, which is marginal, is so adjusted as not to operate in the circuit previously traced in series with relay 107 or in the circuittraced for the Winding; of 320. With resistance 319' in parallel with relay relay 100 operates. The operation of relay 109 opens the locking circuit of relay 110 and relay 110 releases after an interval due to the fact that relay 110 is SlOW to release.

Relay 320 opens the locking circuit of relay 302 and that relay releases as soon as brush 310 encounters an insulating segment of centering commutator The release of relay 30 2 opens the circuit of rip-drive magnet and stops the line tinder on the calling s fz'bscriber s line. it also connects battery through resisLan'ce 328 and its left back contact, lower right and upper left contacts of cam 32st, inner back contact of relay 317, resistance 325, brush 326, and terl'i'illltl'l over conductor 112, windings of cut-otl' relay 102 to ground. llelay 102 operates and releases line relay 101 removing; the calling condition from terminal 380. The release of relay 101 opens the energizing circuit of relay 109 permitting its release as soon as relay 110 releases. The release of relay 101 permits relay 103 to release and also opens the circuit of relay The connection of battery with terminal 8537 marks terminal 113 and the other multiple terminals of calling line 100 in the terminal banks of final selectors With reduced bat tery potential to render the line busy at such final selectors. The re ease of relay 309. closes a circuit from battery through the winding" of sequence switch magnet 300, lower left contact of cam 328, outer right front contact of relay 314, right back con tact of relay 302 to ground. Sequence switch 300 is advanced in this circuit to position 3.

Vhen sequence switch 300 leaves position 2 the circuit of relay ill-"Ii. is opened and that relay releases. lVh-en the sequence switch 300 reaches position 3, the previously traced circuit for relays 503 and 31'? is completed. l-lelay 317, being marginal, does not operate at this time. Relay S operates and closes an obvious circu t for relay 50? which in turn closes a circuit from bat en through xsistance 508, Winding of relay 500, outer L ont contact of relay 50. to around. e av 509 operates and loclrs over its inner i front contact. Relay 50'? closes a cirrelay 510, conductor 53%, to ground, at the i.-1n'er left front contact of relay 5 '4'. It lso closes a circuit from battery, through the Winding and right normal contact of relay 601, normal contact of brush 602 of timing switch 600 and thence to ground over conductor 523i to the inner right front contact of relay 507. The operation of relay 510 closes an obvious circuit for relay 511 rescues which in turn closes a circuit through the left Winding of relay 512. The operation of relay 601 closes a. circuit from batter, through the Winding of relay 603, normal terminal and brush 604 of switch 600, inner left front contact of relay 601 to ground. ltelay 603 operates and closes a circuit through the Winding of steppingmagnet 605, and its back contact, frontcontact of relay 603, brush and its normal terminal, to grou d at the inner left contact of relay 601. magnet 605 operates and steps switch 600 to its tirstterminal. The further ope ation of the timing switch 600 will be (Le-scribed l 'er.

The opera ion of rear 1 E12 ooens the circuit previously traced from cattery, through resistance 501, to relays e06 and 1 07 and these relays release. The release of relay 407 closes a circuit from battery, thr-ough the Winding of sequence switch magnet e00, lower right contact of cam 4-12, back contact ofrelay 40'? to ground. Seq-r 'nce svv'itc'h l00 is advanced to position 4: from which position it is moved to position 5 by means of ground over the lower left contact of cam In position 5 of the link sequence switch 100 the dialing leads and the fundamental circuit leads are cut through directly from the district circuit to the sender circuit. The dialing circuit may be traced from battery, through the left winding of relay 606, conductor col, normal contact or relay 518, sender selector brush 485, and its corresponding terminal, lower contacts of cam ::14, district finder brush 165 and its corresponding terminal, conductor 382, lower contacts of cam 329', winding of relay 330, right back contact of relay 317, line finder brush S31, terminal conductor 116 through the subscriber s substation, conductor 117, terminal 333, brush 33%, middle left back contact of relay 317, 1 ft contact of cam 335, conductor 375, brush e966, and its associated terminal, lower left contact of cam 415, brush 486, and its associated terminal, outer right baclr contact of relay 513 to ground.

ln position 5 of the link circuit sequence switch 400, relays 406 and so? are connected in a circuit extending from brush 48 left contacts of cam 408, Winding of relay 407, right Winding of relay 106, upper contact of cam 41s, to brush Ed. The circuit of these right front contact of relay 610, conductor v 638, upper left contact of cam 516 to ground.

As soon as relay 609 operates the dialing tone circuit is completed as follows: from source of tone 607, right winding of relay 606, normal terminal and brush 804 of register steering switch 800, outermost le'tt con tact of relay 609, conductor 618, lower contact of cam 514, conductor 534, to ground at the inner left front contact of relay 507.

Due to the closure of this circuit a tone is induced in theleft winding of relay 606 and over the dialing circuit to the receiver of the subscribers telephone to indicate that dialing may be started. The subscriber now dials the number of the wanted subscriber.

Gall to subscriber in mechanical ofiice.

It will be assumed that the wanted subscriber is located in an ofiice reached from the district selector and that the number is Warren 4537 which would be equivalent to dialing 924537. The operation of the subscribers dial alternately opens and closes the circuit of relay 606 as many times as there are units in each digit. Relay 606 releases and operates each time this circuit is opened and closed. The first release of relay 606 closes a circuit from battery, through the right winding of .relay 611 and resistance 612 in parallel, windingoi magnet 817, right back contact of relay 613, normal terminal and brush 802 of register control'switch 800,, winding of slow to release relay 614, left-front contact of relay 610, back con tact of relay 606, conductor639, inner right back contact of relay 515 to ground. Relays 611 and 614 and magnet 817 are energized in this circuit.

.At the same time a branch of this circuit extends from battery through the winding of relay 615, over the right contact of relay 609, brush 803 of register control switch 800 and its normal terminal, conductor 808, back contact of magnet 817 right back contact of relay 618 and thence as traced to ground on conductor 639. Relay 615 operates and connects ground from its armatures to the windings of relays 610 and 614 to prevent their premature release it relay 606 makes its front or back contact very briefly. Relay 610 being slow to release holds operated during the short interruptions of its circuit when relay 606 is released. Relay 614 being slow to release also holds operated during the short interruptions of its circuit when relay 606 is energized between dial impulses. It does not hold over, however, during the longer periods between digits.

The. operation of relay 614 closes a circuit from batt ry, through the left winding of relay 611 and resistance 616 in parallel, winding of stepping magnet 807, front contact of relay 614, to ground, Relay 807 attracts its armature but does not step register controlswitch 800 until relay 61.4 is released at the completion of the first digit. Magnet 817 is energized each time that re.- lay 606 makes it back contact and steps the A code register 810 one position for each interruption of the dialing circuit. Since the first digit is 9 register 810 will come to rest in its 9th otl normal position. At the completion of the first digit, relay 614 releases releasing magnet 817 and steps the register control switch to its first of]? normal terminal. \Vith the register control switch 800 in this position the pulsing circuit is extended to the stepping magnet 827 of the B code register 820. The circuit of magnet 827 may be traced from battery through the right winding of relay 611 and resistance 612 in the parallel, winding of magnet 827, brush 802' and its first oil normal terminal, winding of relay 614, left front contact of relay 610, back contact of relay 606 to ground on conductor 639. 'The circuit of relay 615 is also completed at this time from battery, through the winding of that relay, right contact of relay 609, brush 803 and its first off normal terminal, conductor 809, back contact of magnet 827, brush 802 and its first off'normal terminal and thence as traced for magnet 827 to ground. In each successive position of register control switch 800 these two circuits are successively com pleted through the winding and over the back contact respectively, of each of the numerical register stepping magnets.

Since the second digit is 2, the. B code register 820 comes to restin its second off normal position after which register control switch 800 is stepped to its second oil normal position. As soon as switch 800reaches this position a circuit is completed from battery through the winding of relay 617 and its normal contact, brush 804 and its second terminal, outermost left contact of relay 609,- to grounded conductor 618. Relay 617 operates and locks over its innermost front contact to ground on conductor 618. The operation of relay 617 closes a circuit from battery through resistance 818, winding of rotary magnet 843, back contact of magnet 844, outermost front contact of relay 617 to ground; and also from battery, through resistance 819, winding of rotary magnet 858, back contact of magnet 857, next to the outermost contact of relay 617 to ground. The translator 830 consists of two power driven rotary switches which are provided with two sets of brushes, arranged opposite one another. Translators of this type have been disclosed in a number of previous ap plications and reference is made to the patent to A. E. Lundell, No.1,550,377, granted August 18, 1925.

The energization of magnets 843 and 858 rotates the switchesconstituting the. trans-- lator 830. The energization of relay 617 also closes a circuit :from ground on conductor 618 over the outermost leit contact of relay609,back contact'ofrelay 608, nextto the innermost contact of relay 617 "brush 814 and its ninth of? normal terminal, next to the innermost contact ofrelay 828, brush 822 and its second oil normal terminal to -a contact in each set served by translator brush'es83l, 837,645 and-851. Since the A codeswitchSlO is set inzposition 9 a-circuit is also completed from battery, through the winding of relay 829, 9th off .normal terminal a'nd brush 812, right baclr contact of relay {619, register control brush 805 f and its third terminal :to ground. Elie-operation of relay 829, opens the {circuits including brushes 851 and 837 and closes the circuits including brushes '831 -and lllherei'liore the circuits from ground to terminals oi" brushes'831 and 84.5 are extended over the front contacts otrelay-SQ.) to the stop magnets 844l- -and 857 of the translator 830. These :inagnets operate, opening; :the circuit ofcthe rotaryimagnets 8 i3i-and 858 bringing the switches of the translator to on the terminals corresponding to 5 those gro undcd. Circuits are also completed for relays 620 and 621. The circuit of relayllfZO may be traced from battery through its winding, and the right trout @c'ontaet of relay 829 over brush 84511.0 ground on its terminal. The circuit of relay/621 extends from bat-- tery, t-hrmigh its winding, deft front'contact of relay 829, brush 831 and its-terminal to ground. The operation of :relay closes a locking circuit for itself over its inner left contact to ground at the nezrtto the outermost from, contact ot-relayGiT. Ee'layGQl closes a docking circuit for itself over its inner right contact to ground at the outermost QOIIEEL'Cfi Of relay 617. The stop inagnets 857 andSsll 'arealso' held operated in these locking circuits. The operation of relay'620closes a circuit from .ground over tlieterminal'upon whiclrbrush 850 has come to rest, cross connecting =raclr '959, upper right contact of'cam 951,-windinp; ofmagnet 950 andre'l-ay 952 iniparallel tobattery. The class sequenceswitch 950 isadvanced in'this circuit to position l, 9, 13 or 18, each of which. represents the full qmechanical class of call. If'the switch was standing in position '3, for example, it would come to rest in position 4.

il he class sequence switch controls the operation of the sender 'il1." lCCOICl2111C8 with the class of call to beextended. The joint operation of relays-620 and621 closes-a circuit from battery, through the winding of sequence switch magnet 500, lower right contact of cam 517, :outer i635; contact of relay 620, outer left contact of relay 321, upper contact joi cam 518 to ground. 'Sequence switch 500 operates in thiscircuit to advance the Sender control sequence switch to position 2. With theseguenceswitch 50,0 in position 2 the fundamentalcircuit iscompleted from battery, through the left winding of relay 314,10werright contact-of-cam 313, upper right contact of cam 81-2, conductor 87 8, brush 461 audits associated :terminal, upper right and lower left contact of ,cam402, brush 4'81 and-its associated terminal, rightbaclr contact o'frel-ay see, right contact or" earn 701, winding-of steppingirelay 7 02, :back contact ofrela-y 7.03, leftwinich ingot relay 704,1le-tt contact eotwam 7.05, inner right contactofrelay 620,1niddle-lett contact of relay '621, resistance 3623 to ground. Relay-s,- 314 and 702'o'perate in this circuit but relay 704 is polarized and does not. Relay-31d locks through,itsiinneriright iront contact, upper left contact of cam 313, upper right contact :of cam 312, to ithe fundamental circuit as iprevjiously traced. Relay are in operating; also :closes a circuit from battery through the winding -:of sequence switch magnet 300, Elower left contact .ot cam 828, outer right front contact of relay 314, right back contact :of :relay 302 to ground. Magnet 3(90 ienergi-zes :in this circuit andradvances thesequence switch reposition l.

in .position the energizing Gll-Qlllit for relay 3'14: isopened but the lockingicircuit is maintained closed. At ithe same :time .a parallel circuit is prepared from the :inner right :front contact otrelay 314E, upper left contact sot cam 313, upper left contact of cam 31-2, commutator segment I337, zbrush 338, right contacti fcanr339to ground. In position at :relay 314 closes a circuit from battery, through the winding of updrive ma net 3&0, upper right-contact offca'mS lll, outer right trout contact of relay are, back contact of relay 302 to ground. The updrive magnet energizes .in this circuit and causes the district selector switch :sha'l't to move upward in a brush selecting zmoivement. Each time that brush "338 :makesicontact with a conductingsegmentof stripfilii the parallel circuit 'above trace'd is -'c0mpleted, in which circuit relay 31-4 is *held operated and the stepping relay of the sender shunted.

jWhen the fundamental circuit above traced was closed-and stepping relay 'lOil 0perated, it closed a circuit from battery, in-

ier 'le'l't contact of relay 621, left contact of cam 519, winding of the 'Nofi3 counting' relay,'back contact of the No. 3' counting relay, conductor 706, translator brush*849and itscorresponding terminal, right contacts of cam 707, inner left back contact of relay 708, left contact-ofcam 520,'contact of relay 702, lower left contact of eam 518 to ground. The No. '3 counting relay operates in this circuit and locks through the winding ofthe No. 3-counting relay, fron't contact of the No. 3 counting relay, upper right contact of cam 709 to ground. The No. 3"

conducting segment of commutator strip 337, stepping relay 702 is shunted and deenergized, opening the above-traced circuit for the No. 3 counting relay permitting the No. 3 counting relay to operate in the locking circuit of the No. 3 counting relay.

The energization of the No. 3 counting relay connects conductor 706 through the back contact of the No. 2 counting relay to the winding of the v.No. 2 counting relay and thence to battery. When brush 331 encounters an insulating segment the shunt is removed from relay 7 02 and that relay again energizes closing the circuit from ground to conductor 706 causing the energization of the No. 2 counting relay. As the district selector switch shaft continues upward and brush 33S engages the insulating and conducting portions of the commutator segment 337, stepping relay 702 is alternately deenergized and energized and the counting relays successively operated. When brush 333 reaches the fourth conducting segment and stepping relay 702 deenergizes for the fourth time, the 0 counting relay operates in parallel with relay 703 and in series with the No. 0 counting relay. The operation of relay 7 03 opens the fundamental circuit and permits the release of relay 314 as soon as brush 338 leaves the conducting segment. The operation of the 0 counting relay closes a circuit from battery through the winding of sequence switch magnet 700, right contact of cam 710, left back contact of relay 708,, front contact of the 0 counting relay to ground at the inner back contact of relay 7 11. Sequence switch 700 is energized iii this circuit and advances the sender sequence switch to position As soon as sequence switch 700 leaves position 1 the locking circuits of all operated counting relays are opened, releasing such relays. The release of relay314 as previously described opens the circuit of updrive magnet 340 and closes a circuit from battery, through the winding of sequence switch magnet 300, lower right and upper left contact of'cam 342, outer right back contact of relay 314, back contact of relay 302 to ground, in which circuit the sequence switch is advanced to position 5. \Vith sequence switch 300 in position 5 and sequence switch 700 in position 3 the fundamental circuit is again closed from battery, through the left winding of relay 314, lower right contact of can: 313,

.upper right contact of cam 312, conductor 378, thence as previously traced, right back contact of relay 504, right contact of cam 701, winding of relay 702, contact of relay 703, left winding of relay 704, left contact of cam 705, innermost ri ht contact of relay'620, middle left contact of relay 621, resistance (3.3 to ground. Relays 314 and 702 operate in this circuit as before. Relay 314 looks as previously described and closes the previously traced circuit for sequence switch 300 in which circuit the sequence switch advances to position 6. The operation of stepping relay 702 closes a circuit from battery, right contact of cam 519, through the winding of the N0. 1 counting relay, backcontact of the No. l counting relay, conductor 712, translator brush 848, lower right and upper left contact of cam 707, inner right back contact of relay 708, left contact of cam 520, contact of relay 702, lower leftcontact of cam 518 to ground. In positions 5 to 7, inclusive, of sequence switch 300 trip magnet 343 is energized in a circuit extending from battery through its winding, lower rightcontact of cam 336 to ground. W'hen the sequence switch arrives in position 6 updrive magnet 340 is again energized and the district selector switch shaft is moved upward in a group selecting movement. Due to the energization of trip magnet 343 and the positioning of the district selector in accordance with the brush selecting operation just described the fourth brush set is tripped and moved over its corresponding terminals.

'As in the case of brush selection a shunt circuit is prepared extending from ground over the upper right contact of cam 339, brush 344, commutator segment 345, lower left contact of cam 313 to the fundamental circuit as previously traced. As the district selector moves upward the stepping relay 702 will beperiodically shunted and the counting relays operated beginning with the No. 1 counting. relay. lVhen the 0 counting relay operates at the second release of relay 702, relay 703 is operated releasing relay 314 and bringing the district selector to rest" with its brushes engaging the first terminal of the second group to which the fourth brush set has access.

The release of relay 314 also closes a circuit from battery through the winding of sequence switch magnet 300, lower right and upper left contacts of cam 342, outer right back contact of relay 314 to ground at the back contact of relay 302 advancing the sequence switch to position 7.

In position 7 of sequence switch 300, relay 314 is operated in a circuit from bat-- tery through its right winding, upper right and lower left contacts of cam 347, lower left and upper right contacts of cam 308, line finder commutator segment 353, brush 354 to ground. The operation of relay 314 closes acircuit from battery, through the winding of sequence switch-magnet 300,

lower left contact of cum 328, outer right front contact of relay 314, back contact of relay 302 to ground. Sequence switch 300 .is advanced in this circuit to position 8.

In position 7% to 3 relay 314 looks over its left front contact, upper contacts of cam 348, to the sleeve brush 349 and round over the sleeve terminal of the trunk, provided that trunk is busy. The energizing circuit of relay 314 is opened in position 8. If the first trunk of the group is busy and relay 314 is held energized in position 8, a circuit is completed for the updrive magnet 340 from battery, through the winding of the magnet 340, upper right contact oi cam 341, outer right front contact of relay 3 14 to ground at the back contact of relay 302. The updrive magnet is energized and causes the district selector to move upward in search of an idle outgoing trunk. Relay 314 is held operated between terminals over a circuit extending from battery, through its right winding, upper contacts 01 cam 347, commutator segment 384, brush 371, upper left contact of cam 341, outer right front contact of relay 314, back contact 01" relay 302 to ground. As soon as an idle trunk is reached, characterized by the absence of ground on its sleeve terminal, the locking circuit of relay 314 is opened and the relay releases in turn releasing the updrive magnet bringing the district selector to rest on the first idle outgoing trunk of the group. The release of relay 314 closes a circuit from battery, winding of sequence switch magnet 300, lower right and upper left contacts of earn 342, outer right back contact of relay 314, back contact of relay 302 to ground advancing the sequence switch to position 9.

As soon as relay 314 releases, ground is connected to sleeve terminal 383, over the upper left contact of cam 339, inner right back contact of relay 314, right contacts of cam 350, through sleeve brush 349, to render the selected trunk busy. As soon as the sequence switch arrives in position 8% ground is connected over the lower contacts of cam 350 and sleeve brush 349, to sleeve terminal 383, independent of relay 314, which ground is maintained until the sequence switch leaves position 15%.

Nith sequence switch 300 in position 9 a circuit is completed from battery through the winding of relay 351, lower right contact o't cam 316, conductor 315, to brush 464 and its associated terminal, and thence through the right winding of relay 406, and the winding of relay 407, to brush 484 and its associated contact as previously traced. From brush 484 this circuit is extended over conductor 506, right back contact of relay 505, inner left contact of relay 504, middle and right windings of relay 503 to ground. A parallel circuit is also closed through the left winding of relay 317, left contact of cam 316 and thence as traced for relay 351 to ground. Relay 351 operates in this circuit, but relay 317 being marginal does not. The operation ot' relay 351 closes a circuit from battery, through the right winding of relay 314, lower right and upper left contacts 0t cam inner contact ol relay 351, line finder commutator segment 353, brush 354 to ground. Relay operates and closes a circuit frombattery, through the winding oi sequence switch magnet 300, lower left contact 01' earn 323, outer right front contact of relay 314, back contact of relay 302 to ground. Sequence switch 300 is advanced in this circuit to position 10 in which position it remains during subsequent selections.

Since the call was to an otlice reached directly through a district selector without passing through an oiiice selector relay 711 was operated as soon as sequence switch 700 reached position 2 in a circuit from battery through the winding of relay 711, lower left and upper right contacts of cam 714, translator brush 836 and its corresponding terminal, outer le'tt contact oi relay 621, up per contact of cum 513 to ground. Relay 711 operates and closes a circuit from battery, hrough the winding of sequence switch magnet 500, upper left contact of cam 521, trout contact of relay 711 to ground. Sequence switch 500 is advanced in this circuit to position 7.

hen sequence switch 500 leaves position 6, relay 711 is deenergirzed. As long as relay 711 is operated sequence switch 700 is prevented from leaving position 3. When the 0 counting relay has operated and relay 711 has closed its back contact a circuit is closed from battery, through the winding of sequence switch magnet 700, right contact of cam 710, back Contact of relay 7 08, contact of the 0 counting relay, back contact of relay 711 to ground advancing the sequence switch to position 4. lVhen sequence switch 500 reaches position 7 a circuit is closed from battery through the winding of sequence switch magnet 700 upper left contact of 715, lower left contact of cam 522 to ground advancing the sequence switch to position 5 in which position incoming selections are made.

.Vith sequence switch 500 in position 7 and sequence switch 700 in position 5 the trunk leading to the wanted office is tested. It the incoming selector associated with the trunk selected by the district selector has been released from a previous call but has not yet returned to normal, 24 volt battery is connected to the tip conductor, but if the incoming selector is normal, 48 volt battery is connected through a relay of the incoming selector to the tip conductor. With the sequence switches 500 and 700 in positions 7 and 5, respectively, the fundamental cirliE-i) cuit is closed from ground (not shown) at the incoming selector 1101, over the ring conductor 1108, terminal 385, brush 355, upper left and lower right contacts of cam 356, conductor 379, brush 162 and its corresponding terminal, upper right and lower left contacts of cam 40 1, brush $82 and its corresponding terminal, inner left front contact of relay 507, outer left contact of relay 52%, compensating resistance 859, brush'832 of translator 830, lower contact of cam 525, left winding of relay 704;, winding of relay 716, lower left contact of cam 717, resistance 718, lower contact of cam 719, left contact of cam 95 1, upper right contact of cam 523, right back contact of relay 504-, brush 4:81 and its corresponding terminal, lower left and upper right contacts of cam 402, brush 41-61 and its corresponding terminal, conductor 378, left back contact of relay 359, upper contacts of cam 358, brush 357, terminal 386, over tip conductor 1109 of the trunk to battery (not shown) at the incoming selector 1101. Assuming that the incoming selector is in its normal condition relay 716 operates closing an obvious circuit for relay 720 which also closes an obvious circuit for relay 721.

Relay 721'locks from battery, through its winding, inner right contact, upper left contact of cam 722 to ground. The operation of relay 721 also closes a circuit from battery through the winding of sequence switch magnet 700, lower right contact of cam 715, right contact of cam 955, outer right front contact of relay 7 21, to ground at the inner hack contact of relay 711. Sequence switch magnet 700 is energized in this circuit advan ing the sequence switch to position 6. Relay 721 releases as soon as switch 700 leaves position 5. If the incoming selector had not been normal, and only 24 volt battery included in the fundamental circuit as above traced the presence of resistance 713 would have prevented the operation of relay 716. This resistance also prevents the operation of the incoming selector relay during trunk testing; When switch 700 reaches position 6' the fundamental circuit is closed as previously traced'through the winding of relay 7 0 t, and thence over the back contact of relay 703, through the winding of stepping relay 702, upper left and lower right contacts of cam719, upper contact of cam and thence as previously traced to battery at the incoming selector circuit. Incoming brush selections are now accomplished in the same manner as district brush selections, except that the counting relay circuit extends from battery, over the right contact of cam 519, winding of the N0. 2 counting relay, back contact of the No. 2 counting relay, conductor 723, to the #4 terminal and brush 1 03 thousands register 1000. upper contacts of cam 7 24, outer right contact of relay 7 526, inner left back contact of relay 708, left contact of cam 520, contact of relay 702, lower left contact of cam 518 to ground.

At the completion of incoming brush selection the 0 counting relay and relay 703 are operated as before. The operation of the 0" counting relay advances the sequence switch700 to position 8 for incoming group selection. As the sequence switch leaves position 6 4 all operated counting relays are released, their holding circuits being opened at cam 709. Itshould be noted at this time that'since hundreds register 1010 is set inposition 5, a circuit is closed from battery, through the winding of relay 1008 lower left contact of cam 956, No. 5 terminaland brush 1013 to ground. Incoming group selection takes place in the same manner as incoming brush selection except that the countingrelay circuit extends from battery, over the right contact of cam 519 through the winding of the No. 1 counting relay, back contact of the No. 1 counting relay, conductor 712 to the outermost front contact of relay 1008, N0. 4 terminal and brush 1004 of thousands register 1000, right contacts of cam 724:, and thence as traced for incoming brush selection to ground.

At the completion of incoming brush selection the operation of the 0 counting relay advances sequence switch 700 to position 10. As the sequence switch leaves position 8 all operated counting relays release, their holding circuits being opened at contacts of cam 709. During the time that. switch 700 is advanced from position 8 to 10 the incoming selector hunts for and selects an idle final selector associated with the wanted group of lines. While switch 7 00 is passing through position 9 the fundamental circuit is again closed through resistance 718, upper contact of cam 717, lower cont-act of cam 525, through compensating resistance 859 and thence as previously traced to ground for the purpose of discharging the trunk circuit before making final selections in order that rela 702 may not be falsely operated by the discharge of the line. When switch 700 reaches position 10, the fundamental circuit is closed through the control relayof the final selector 1102 and final brush selection is made in a manner similar to incoming'brush selection except that the circuit for the counting relays extends from battery, over the right contact of cam 519, through the winding of the No. 0 counting relay, back contact of the N0. 0' counting relay, conductor 732 to the No. 5 terminal and brush 101 1 of hundreds register 1010, upper right contact of cam 726, upper right contact of cam 724, outer right contact of relay 526, inner left back contact of relay 708, leftcontact of cam 520, contact of relay 7 02, lower left contact of cam 518 to ground.

At the completion of the finalbrush selec- 

